Electric discharge tube



NOV. 25, 1952 DIEMER ELECTRIC DISCHARGE TUBE Filed July 28, 1949 nus Diegmer AGE T Patented Nov. 25, 1952 ELECTRIC DISQHARGE TUBE Gesinus Diemer, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 28, 1949, Serial N 0. 107,286 In the Netherlands August 19, 1948 3 Claims. 1

This invention relates to electric discharge tubes of the travelling wave type for generating, amplifying or modulating waves of wave length several decimeters or less, also and to apparatus embodying such discharge tubes.

Known travelling wave tubes comprise a cylindrical helix within which travels an electron beam. They have a limitation in that the linear electron beam can carry little current only,

so that the tube is not capable of producing high energies. Furthermore, an intensive magnetic field is required to concentrate the beam. The invention provides a travelling wave tube of different type which is capable of operating with high current and which has additional advantages.

According to the invention, in a device for producing, amplifying or modulating waves of wave length of the order of several decimeters or less, comprising an electric discharge tube of the travelling wave type, this tube comprises a cylindrical cathode, one or more cylindrical controlor screen-grids and surrounding them a gridshaped electrode, the section of which at right angles to the axis of the cathode is a spiral, the whole electrode system being surrounded by an anode.

In order that the radial speed of the electron beam and the speed of the wave may be identical, the ratio between circumference and the pitch of the spiral must have a constant value.

The spiral electrode is therefore preferably made as a logarithmic spiral, the apertures in the spiral grid-electrode are also arranged so that when viewed from the cathode the apertures in the various turns line one behind the other and in line with the apertures in the controlor screen-grids.

The starting pitch of the spiral is preferably chosen to be small compared with the starting radius, whilst the optimum ratio between internal radius and external radius is equal to e, the base of the natural logarithms. The spiral thus satisfies the equation T =T7I in which a is the starting pitch, n the starting radius, 1'1; the radius of the n turn and n, integer or fraction, the number of turns traversed from the beginning. If the voltage of the spiral electrode relatively to the cathode is V volts, the relation which applies for the maximum number of turns at which the tube can still be operated eiTectively is In order that the invention may be more clearly understood and readily carried into effect, one example will now be described with reference to the accompanying drawing, in which:

Fig. 1 is a sectional view of the tube, taken at right angles to the axis of the electrode system, and

Fig. 2 a vertical sectional View, partly in elevation, taken through the axis of the tube. The tube is shown at twice its full size.

Referring to the figures, l designates the glass wall of the tube, in the axis of which is arranged a cylindrical hot cathode 2 of 5 mms. diameter. The hot cathode is surrounded by a control-grid 3 and a screen-grid 4. The spiral electrode 5 is made of six narrow molybdenum strips 1 which are wound about eight series of stay rods to form a logarithmic spiral. Viewed from the cathode. the stay rods for the spiral electrode lie behind the stays of the controland screen-grids, which are provided with circular rings corresponding with the strips 1. The starting radius of the spiral is'9 mms. and the starting pitch 1.1 mm. During operation the spiral electrode is given a voltage of V relatively to the cathode and the anode 6 a voltage of 100V also. The anode G is formed by a cylindrical metal ring. The tube is intended for use in producing oscillations of about 30 cms. wavelength.

What I claim is:

1. An electron discharge tube of the traveling wave type comprising a cathode, a grid located in the path of the electron emission from said cathode, a, traveling wave conductor encircling said grid with a pluralityof turns and having a spiral section at right angle to the axis of the cathode, and an anode surrounding said conductor, the radius Tn for the n turn of the spiral conductor being equal to ill? flue n in which a is the starting pitch and n is the starting radius.

2. An electron discharge tube of the traveling Wave type comprising a cathode, a grid located in the path of the electron emission from said cathode, a traveling wave conductor encircling said grid and having a spiral section at right angle to the axis of the cathode, the ratio between the largest radius and the smallest radius of the spiral conductor being equal to e, the base of the natural logarithms, and an anode surrounding said conductor.

3. An electron discharge tube of the traveling wave type comprising a cathode, a grid located in the path of the electron emission from said 3 cathode, a traveling wave conductor encircling said grid with a plurality of turns and having a spiral section at right angle to the aXis of the cathode, the number of turns N and the operating voltage V of the spiral conductor being in the relationship N=s0V-* and an anode surrounding said conductor.

GESINUS DIEMER REFERENCES CITED The following references are of record in the file of this patent:

Number Number 4 UNITED STATES PATENTS Name Date Grebel Feb. 10, 1931 Jonker Mar. 30, 1937 Charton s Jan. 25, 1949 FOREIGN PATENTS Country Date Germany May 4, 1932 

